Who is the main villain in Diablo 2?

As an ardent Diablo franchise fan, I‘ve played through the games more times than I can count. And without a doubt, the iconic Lord of Terror Diablo stands out as the foremost villain driving the chaos and mayhem in Diablo 2. But his equally sinister Prime Evil brethren Mephisto and Baal also play critical roles, making the answer more complex than you might expect.

Diablo rules as the central villain

When I first battled the encroaching darkness in Diablo 1, Diablo was clearly established as the sole Prime Evil and ultimate bad guy. After his soul stone imprisonment, this demonic force of chaos wasted no time in corrupting the land and people of Khanduras from within his underground prison.

Once his soul stone containment is shattered, Diablo returns as the sweeping epic villain directing the havoc across Sanctuary. And in Diablo 2, not much changes – the Lord of Terror‘s essence persists as the central driving force behind the Prime Evils‘ onslaught.

So why does Diablo stand out as the foremost villain in Diablo 2?

• He originated the Prime Evil concept as the seminal villain in Diablo 1
• His essence persisted through his soul stone to unleash chaos in Diablo 2
• He corrupted his host Aidan to become the Dark Wanderer
• Diablo masterminded the strategy to reunite the Prime Evils
• His terror demon form remains the most iconic villain visual
• Defeating Diablo himself is the ultimate goal across all acts

So while his brothers Mephisto and Baal may direct major destructive schemes, it is Diablo‘s soul and demonic spirit that originated the threat and serves as the common thread weaving through every act.

In the final cinematic, the narration says it all:

"And there was one soul that still lived within that hell – Diablo, Lord of Terror and survivor of the Dark Exile. No one knew for sure how long he had been living in that infernal realm, not even him…"

The supporting villains: Mephisto and Baal

As the franchise expanded in scope for Diablo 2, so did its villains. Mephisto (Hatred) and Baal (Destruction) emerged not just as fellow Prime Evils, but critical villains in their own right directing major plots across various acts.

Mephisto‘s Schemes

As the Lord of Hatred, Mephisto masterminds the corruption of the Zakarum faith and their fanatical crusades across the lands of Kehjistan in Act III. His lair is the hellish Chaos Sanctuary, and Mephisto even seizes the souls of the Zakarum faithful, using them to fuel his power.

Baal‘s Destructive Agenda

Meanwhile, Baal focuses his efforts on attacking Mount Arreat and the sacred Worldstone. His destructive schemes culminate in corrupting the Worldstone – which could have far worse implications than just laying waste to Arreat‘s icy mountain fortress.

So Mephisto and Baal direct massive destabilizing events central to Acts III and V. While Diablo may have originated the threat, his brothers‘ actions also further the Prime Evils‘ united front to unleash chaos.

Diablo 2 Prime Evils – United They Wreak Havoc

And in the final cinematic, Tyrael refers to the defeat of all Three Prime Evils, not just Diablo – showing just how critical they were as a triad of ultimate villains:

"…you have accomplished the impossible; Diablo and Mephisto have been banished back into the Black Abyss that spawned them and the corrupted Worldstone has been destroyed."

So while Diablo stands supreme as the foremost villain and impetus between both games, Mephisto and Baal also play critical support roles furthering the Prime Evils‘ united chaos and destruction across Sanctuary.

The Lesser Evils complicate things

The villain hierarchy expands further in Diablo 2 with the introduction of the Lesser Evils – the four secondary demon lords named Duriel, Andariel, Belial and Azmodan. So how do these new villains fit into the picture?

The Lesser Evils assist the Prime Evils‘ plans

After the Prime Evils were exiled to Sanctuary, it turns out they weren‘t the only demons to make the journey. The Lesser Evils also managed to take up residence in Sanctuary and pledge support to their Prime Evil masters:

• Andariel oversees the Chaos Sanctuary for Diablo
• Duriel acts as Mephisto‘s Maggot King guarding Tal Rasha‘s tomb
• Belial shapeshifts to disguise himself and spread Mephisto‘s lies
• Azmodan commands Diablo‘s siege on Bastion‘s Keep

So in their quest for power, the Lesser Evils directly assist the Prime Evil brothers‘ major schemes across Acts I-IV. They serve critical support roles enacting the overarching plans.

Each Lesser Evil plays the main villain within their dedicated act

So while the Prime Evils drive the central plot, it is the Lesser Evils that serve as the direct act bosses to beat at the climax of each act:

• Act I – Darken the lands by defeating Andariel
• Act II – Free Tal Rasha‘s tomb by killing Duriel
• Act III – End Mephisto‘s lies by destroying Belial
• Act IV – Vanquish hell‘s siege by killing Azmodan

So in some ways, each Lesser Evil serves as the short-term "main villain" with their final climactic boss fight. But they are simply supporting minions enacting their Prime Masters‘ overarching game-spanning plans.

In summary – Prime Evils drive overall plot; Lesser Evils act as Act Bosses

Diablo‘s legacy as the ultimate villain

Reviewing how the villains and acts unfold in Diablo 2, it gives me renewed appreciation for how complex the hierarchy of evil formed. While Diablo originated the threat and serves as the common impetus across both games, his fellow Prime and Lesser Evils all played critical support roles in spreading terror and chaos across Sanctuary.

But having played all games extensively, I still consider the iconic Lord of Terror Diablo himself as the undisputed main villain and ultimate threat in Diablo 2 based on:

• His original establishment as sole villain in Diablo 1
• Persisting as central threat through Aidan in Diablo 2
• Corruption across Acts I-V driven by his essence
• Climactic final boss fight vs. Diablo to save Sanctuary
• Enduring legacy as the face of evil in Diablo universe

For ardent fans like myself who‘ve followed this epic struggle between good and evil across 20+ years now, Diablo‘s distinct horned silhouette and flowing red vestments will forever represent the face of terror and chaos across the realm of Sanctuary.

So while various demon lords have come and gone, the Lord of Terror Diablo stands out clearly as the foremost villain we‘ve been hunting across two decades now. I for one can‘t wait to see his surprise return teased in Diablo 4!